
import java.util.*;
public class amin3 {
    public static void main(String[] args) {
        long[] fib = new long[80];
        fib[0] = 1;
        fib[1] = 1;
        for (int i = 2; i < 80; i++) {
            fib[i] = fib[i - 1] + fib[i - 2];
        }
        Scanner s = new Scanner(System.in);
        while (s.hasNextInt()) {
            int from = s.nextInt();
            int to = s.nextInt();
            long count = 0;
            for (int i = from - 1; i <= to - 1; i++) {
                count += fib[i];
            }

            System.out.println(count);
        }
    }
}